1. Field of the Invention
The present invention relates to an electronic circuit unit that includes a metal housing and a circuit board which is housed in the housing and to which a connector is secured.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2002-314264 describes an invention relating to a casing that houses an electronic component. This casing includes a casing body that includes an upper casing body and a lower casing body which are formed of metal. A printed circuit board to which a connector is secured is housed in the casing body.
An upwardly extending elastic engagement piece is formed in the lower casing body. The engagement piece is brought into engagement with a recess portion formed in the printed circuit board. When the upper casing body is combined with the lower casing body, the elastic engagement piece is swaged and secured to the upper casing body and an edge portion of the printed circuit board is pinched between a pressing portion of the upper casing body and the lower casing body.
In a casing that houses a printed circuit board to which a connector is secured, a large force acts on the connector when a plug is fitted into or removed from the connector. This force is transmitted from the connector to the printed circuit board. Thus, by repeatedly fitting and removing the plug into and from the connector, a problem in that a conductive pattern and soldered portions formed on the printed circuit board are damaged or is likely to occur.
With the casing described in Japanese Unexamined Patent Application Publication No. 2002-314264, part of the printed circuit board is only pinched between the lower casing body and the upper casing body. Thus, when a large force is repeatedly applied to the connector, large stress is likely to act on the printed circuit board.
Furthermore, since the mass of a connector secured to the circuit board is comparatively large, the circuit board is likely to be moved in the casing. In the case of on-vehicle equipment, the circuit board is likely to rattle. According to the structure described in Japanese Unexamined Patent Application Publication No. 2002-314264, the printed circuit board is pinched between the upper casing body and the lower casing body. Thus, the printed circuit board is likely to be moved in the casing body.
It is conceivable to use alternative related art with which a printed circuit board is secured to a casing by screws so as to reduce the likelihood of bending stress acting on the printed circuit board. However, with this structure, the number of man-hours for screwing in assembly is increased. Furthermore, a space for screwing is required. Thus, it is difficult to reduce the size.